I see it all the time doing shakedowns and never realy pay too much attention since it ia all over the place. The people making all the art work are usually people paying off debts or using it as payment for 'rent'.
The ones that have been labled or admitted to as associated with one gang usually have tats of other monikers in other parts of thier bodies. Makes me wonder if they know what it really means either, it is as if they see soemthing cool and all want to copy it and use it in thier own way. The die hard followers/shot callers of a certain gang will take offense and might arrange cause to require the non associated to remove (cut out or burn off) the tat off them or stay off the yard, unless they can pay 'rent' or whatever (and remain indebted forever since they will be labled). Kinda hard to do if your neck, chest or back of your bald head have a 13 or 18 or whatever there. Most of the older gangs are being pushed out due to the younger bangers coming on the scene have no 'code' to follow and are more dangerous since they have no strong leadership enforcment to keep them in check as the older ones are getting weaker in thier age and control starts to slip, so the younger ones just take agressive action on thier own and hope to be noticed by a group they want to be noticed by to get respect
The last gangs class we took showed me that the tracking of all this and trying to break it down left me looking for more scratch paper to keep up. With something like 10-15ish major latino gangs in our area you then had to break them down to all the sub sects inside that where they will form alliances with other sub sects in a major STG grouping that when you were done they were almost one in the same. Kinda like one of them Monty Python plumbing skits where all the pipes go all over the place.
I really love the drawings of some 'ubber tuff' looking dude with a clown nose and his hoe with stupid 'joker' face paint on. OOOoooohhhh.
Since this is long winded and I gotta get to bed my .02$ is over...
We just confiscate them and turn them over to the intel guys so they can keep the players updated as to thier STG.